The Leviathan gas field is a large natural gas field located in the Mediterranean Sea off the coast of Israel, 47 kilometres (29 mi) south-west of the Tamar gas field.[1] The gas field is located roughly 130 kilometres (81 mi) west of Haifa in waters 1,500 metres (4,900 ft) deep in the Levantine basin, a rich hydrocarbon area in one of the world's larger offshore gas finds of the past decade.[2][3][4] According to some commentators, the gas find has the potential to change Israel's foreign relations with neighboring countries Turkey and Egypt.[5] Together with the nearby Tamar gas field, the Leviathan field is seen as an opportunity for Israel to become a major energy player in the Middle East.[6]

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The initial discovery well, Leviathan 1, was first drilled to a depth of 5,170 metres (16,960 ft). The deposit found was estimated to contain 16 trillion cubic feet (450 billion cubic metres) of natural gas.[7] The cost of drilling the discovery well was 92.5 million dollars.[8] The well was drilled by Noble's Homer Ferrington rig.[9]

The second stage of drilling of the Leviathan 1 well was intended to reach a depth of 7,200 metres (23,600 ft), which would include an additional natural gas reserve and potentially 600 million barrels of oil.[10] While the gas discovery at -5170m was made in the Tamar sands layer which was already known to contain gas in other geological formations of the same type in the region, the additional oil and gas potential exists in a deeper layer which dates back to the Mesozoic era and which to date has not been explored in the Levant basin. Noble has twice failed to reach the deeper layer due to technical challenges with drilling to the extreme depths involved. However, during drilling towards the intended target some tell-tale gas signs of possible thermogenic origin were detected and therefore Noble intends to return to the drill site after it obtains the necessary equipment to handle the extreme pressures it previously encountered.[11] A specialized ship under construction in South Korea will begin carrying out the oil exploration effort at Leviathan by the end of 2013.[12] While the probability of finding oil or gas in this unexplored layer is thought to be very small, were they to be found, it would also greatly increase the probability of finding additional hydrocarbon resources in similar ultra-deep geological formations located elsewhere in the region.

The Leviathan gas field is the largest gas field in the Mediterranean Sea and the largest discovery in the history of Noble Energy. Noble Energy operates Leviathan with a 39.66% working interest; Delek Drilling holds 22.67%; Avner Oil Exploration holds 22.67%; and Ratio Oil Exploration holds the remaining 15%.[3] In February 2014, Woodside Energy agreed to buy a 25% stake of the Leviathan field for up to US$2.55 billion.[13] It was announced on 21st May 2014 that Woodside Petroleum pulled out of an agreement to take a stake worth up to $2.7 billion in Israel's flagship Leviathan gas project, as the group developing the field shifted focus to regional markets.

In the summer of 2014 Netherland Sewall & Associates (NSAI) made an upward revision on the amount of gas reserves. The expected year of production was stated to be 2017.[14]

After discovery of the Leviathan gas fields in 2010, Lebanon initially argued that the field extends into Lebanese waters. This was because Israel have agreed with Cyprus on their maritime borders without including Lebanon in the negotiations, a move that Lebanon consider contradictory to previous agreements between the three countries. Lebanon’s Parliament Speaker Nabih Berri stated that Israel is “ignoring the fact that according to the maps the deposit extends into Lebanese waters,” Agence France-Presse reported on June 9.[15] Israeli Minister of National Infrastructures Uzi Landau responded “We will not hesitate to use our force and strength to protect not only the rule of law but the international maritime law,” in an interview. Robbie Sable, a professor of international law at Jerusalem’s Hebrew University, has stated that the claim may be complex due to Lebanon's border with Israel being indented, making it harder to establish Israel’s sea boundary ends and Lebanese waters begin.[15]

In August 2010, Lebanon submitted to the United Nations its official view regarding the maritime border, indicating that it considered the Tamar and Leviathan gas fields to be outside Lebanese territory (though it indicated other prospective fields in the region may be within Lebanese territory). The US expressed support for the Lebanon proposal.[16]